On Thu, Mar 27, 2014 at 10:37:32AM -0700, Jesse Gross wrote: > On Thu, Mar 27, 2014 at 10:33 AM, Flavio Leitner <f...@redhat.com> wrote: > > On Thu, Mar 27, 2014 at 10:19:23AM -0700, Pravin Shelar wrote: > >> On Thu, Mar 27, 2014 at 7:05 AM, Flavio Leitner <f...@redhat.com> wrote: > >> > There are two problematic situations. > >> > > >> > A deadlock can happen when is_percpu is false because it can get > >> > interrupted while holding the spinlock. Then it executes > >> > ovs_flow_stats_update() in softirq context which tries to get > >> > the same lock. > >> > > >> > The second sitation is that when is_percpu is true, the code > >> > correctly disables BH but only for the local CPU, so the > >> > following can happen when locking the remote CPU without > >> > disabling BH: > >> > > >> > CPU#0 CPU#1 > >> > ovs_flow_stats_get() > >> > stats_read() > >> > +->spin_lock remote CPU#1 ovs_flow_stats_get() > >> > | <interrupted> stats_read() > >> > | ... +--> spin_lock remote CPU#0 > >> > | | <interrupted> > >> > | ovs_flow_stats_update() | ... > >> > | spin_lock local CPU#0 <--+ ovs_flow_stats_update() > >> > +---------------------------------- spin_lock local CPU#1 > >> > > >> > This patch disables BH for both cases fixing the deadlocks. > >> > >> This bug is already fixed in OVS. > > > > Could you point me to the commit? I am not finding anything > > recent. > > This is the commit: > > commit 9d73c9cac76ba557fdac4a89c1b7eafe132b85a3 > Author: Pravin B Shelar <pshe...@nicira.com> > Date: Tue Dec 17 15:43:30 2013 -0800 > > datapath: Fix deadlock during stats update. > > I thought that I had sent it in the most recent batch of changes for > net but it looks like I missed it.
That commit is incomplete. Look at the scenario #2 which I explain why it is needed to disable bh for all cpus and not just local ones. fbl _______________________________________________ dev mailing list dev@openvswitch.org http://openvswitch.org/mailman/listinfo/dev
